1. Field of the Invention
The present invention generally relates to real-time, live video production systems, and more particularly to a method, system and device for providing mixing and layering capabilities to outputs of a Video Production Switcher.
2. Discussion of the Background
A video production switcher (or switcher) is an apparatus which combines a plurality of video input signals through various means to provide a plurality of video output signals. Each of the output signals includes a composition of one or more of the input signals and other visual elements generated within the switcher. The switcher generally includes a control panel and a number of video processing circuits.
The video processing circuits of the switcher are generally grouped into functional elements. These elements include Mix Effects (M/E) or Multi-Level Effects (MLE). Each M/E includes a number of Keyers. A keyer is a circuit element which allows one video signal to be layered onto another video signal, with transparency of the former determined by a third video signal (referred to as an Alpha signal). Thus, the M/E is capable of combining a number of video signals by layering one video signal upon another in a prioritized sequence.
This layering can be either a background transition (where one full-screen image is revealed underneath another full-screen image), or a key (where one video image covers a portion of another, through use of a transparency signal, or alpha). Typically, an M/E is capable of one or two background transitions, and between 2 and 4 keys simultaneously. The Mix Effect outputs several outputs, which include a combination of the background mixes and keys. A switcher can have one or more M/Es, and can cascade one into another to allow a greater number of video signals to be layered into a final composite image.
The switcher is also capable of routing video signals from its inputs or Mix Effects to some of its output connections, usually through a video switching matrix. These general-purpose video output channels are referred to as Auxiliary Buses, or Aux Buses. A simple Aux Bus is illustrated in FIG. 4. As illustrated in FIG. 5, Aux Buses can also include timing circuitry (502) to allow alignment of its output to be synchronized to a specified reference (505), regardless of the relative alignment of the selected input signal. This is referred to as a Timed Aux Bus.
One or more Mix Effect units can be used to generate the desired program content. This would include switching and mixing between primary video inputs, such as cameras, videotape, satellite feeds, and so on. Additionally, other elements can be layered over these background selections, such as titles, logos, and the like.
In some situations, it is desirable to produce more than one program from the switcher. Often, these outputs can be similar, with only a slight difference in the additional layered elements. Conversely, a completely different layered composition may be required. In either case, one or more Mix Effects units can be allocated to each of these tasks. Examples of these additional programs include: an output with titles in a second language or outputs to stage monitors. These outputs can also be as simple as a single video background branded with a logo.
This approach presents a problem, however, as there are a small, finite number of Mix Effects units available in the switcher. A switcher will generally have between one and four Mix Effects units. This, combined with the fact that it is often desirable to cascade multiple Mix Effects to create more complex effects, leaves the flexibility of multiple feeds from the switcher quite limited.